A4 Quattro Sedan L4-1.8L Turbo (ATW) (2000)
A/C Signal: Testing and Inspection
A/C Compressor Shut-off, Checking
NOTE:
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The A/C compressor signal communicates to the ECM that the compressor will be switched on in 140 ms.
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The Engine Control Module (ECM) can switch off the A/C compressor via the same wire connection.
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Engine Control Module (ECM) switches off A/C compressor:
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during hard acceleration (Wide Open Throttle 1st gear)
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in emergency mode (emergency operation)
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after initiating basic setting (function 04)
Test requirements:
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A/C system OK
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No DTCs in DTC memory of Engine Control Module (ECM).
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Vehicle at room temperature (warmer than +15 °C).
Test sequence
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Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word". Engine must run at idle.
Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks" See: Testing and Inspection
When indicated on display
Rapid data transfer
HELP
Select function XX
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Press buttons -0- and -8- to select "Read Measuring Value Block" and press -Q- button to confirm input.
When indicated on display
Read measuring value block
Q
Enter display group number XXX
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Press buttons -0-, -5- and -0- to select "display group number 050" and press -Q- button to confirm input.
Indicated on display(1 to 4 = display fields)
Read Measuring Value Block 50
->
1
2
3
4
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Switch A/C system off.
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Specified value in display field 4: Compr. OFF
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Switch A/C system on using "Auto" button and adjust A/C system to maximum cooling or heating power. Compressor must run.
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Specified value in display field 4: Compr. ON
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Depress gas pedal completely (swiftly) and then release it (brief acceleration).
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Specified value in display field 4: Indication jumps for a few seconds from "Compr. ON" to "Compr. OFF" (compressor is switched off when
vehicle accelerates).
If indications do not resemble description:
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Connect VAG1598/31 test box at wiring harness to Engine Control Module (ECM), do not connect ECM. Refer to "Scan Tool Testing/Wiring and
Component Testing Using VAG1598/31 Test Box", See: Testing and Inspection
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Check following wire connection for open circuit and short circuit to Ground (GND) and B+:
Test box VAG1598/31
A/C control head -E87-
Socket
Terminal
41
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Repair open circuit or short circuit if necessary.
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If there are no malfunctions in the wiring, check function of A/C system.